Method of evacuating, filling, sealing, and releasing gas in a container



Aug. 25, 1953 J N. BURDICK ETAL 2,649,993

METHOD OF EV ACUATING, FILLING, SEALING, AND RELEASING GAS IN ACONTAINER Filed Feb. 14. 1947 INVENTORS JOHN N. EURO/CK BY HARVEY E.K/NNE ATTORNEY Patented Aug. 25, 1953 CUATIN G, FILLING,

METHOD OF EVA SEALING, AND A CONTAINER RELEASING GAS IN John N. Burdick,Kenmore, and Harvey E. Kinne, Lockport, N. Y., assignors, by mesneassignments. to Union Carbide and Carbon Corporation, a corporation ofNew York Application February 14, 1947, Serial No. 728.670

1 Claim.

This invention relates to a novel container or bulb for storing andtransporting rare gas, such as neon, ar on. krypton, and Xenon, and toimproved methods of filling, sealing, and releasing gas in a rarecontainer. The invention also concerns the resulting novel package ofrare gas as well as a novel fluid-tight seal that is especiallyadvantageous for sealing a rare gas bulb but is also useful for sealingtubular fluid passages connected to other types of containers.

Rare gas such as neon, argon, krypton, and xenon usually is stored andtransported in small glass bulbs each containing about one liter of thegas. Heretofore, the empty bulb has been formed with tubular glassconnections: one at its bottom through which the bulb is firstexhausted, then filled with the rare gas, whereupon this connection ispermanently sealed by fusing its outer end; and another connection atthe top of the bulb operable to release the rare gas when needed and tolead it into a suitable manifold or receptacle for use. This top gaswithdrawal connection comprises a bulb-sealing glass capsule disposedwithin one end tube, the adjoining open ends of the capsule and thedischarge tube bein permanently united to one another and to a topopening in the glass bulb. When the rare gas is to be released from thebulb, a small steel ball or steel-containing weight is placed in thedischarge tube, the latter is first evacuated to the atmosphere and thenconnected to a rare gas receiver, whereupon the weight is lifted by asuitable magnet and then released to drop on and break the sealed end ofthe capsule. thereby permitting the rare gas to flow from the bulbthrough the discharge tube into the receiver.

The container just described is expensive to manufacture because thedischarge tube and the fragile glass sealing capsule must be welded inplace by an experienced glass blower. Also, premature fracture of thecapsule and loss or contamination of the rare gas sometimes occurs whenthe breaking weight is placed in the discharge tube. Furthermore, if thecapsule is not broken with sufficient care and at the proper moment, thebreaking weight sometimes fractures other parts of the container and thegas escapes. Another possibility of breakage and loss of the rare gasoccurs if the rare gas bulb is sparked when the breaking ball or weightis in place, since the spark occasionally jumps from the discharge tubeto the ball and then to the capsule, which invariably punctures thelatter and eventually results in evacuating all of the rare gas into theatmosphere,

of a glass discharge The principal objects of this invention are: toprovide a rare gas bulb or container which is less expensive toconstruct and simpler and more reliable in use than prior rare gasbulbs; to provide a dependable fluid-tight conduit seal which is formedeasily and economically, is unaffected by wide temperature variations,and may be readily broken when desired without fracturing elementsassociated with the seal; to provide simpler procedure for filling,sealing, and releasing rare gas in containers therefor; and to provide apackage of rare gas which is free from objectionable features of therare gas packages in use heretofore.

The above and other objects and novel features of the invention willbecome apparent from the following description and the accompanyingdrawing. In the drawing:

Fig. l is a side elevational view of a rare gas bulb, parts being brokenaway and in section, ready for sealing by the method of the invention;

Fig. 2 is an enlarged perspective view of one type of fusible metal sluguseful for forming a flu d-tight seal by the novel method;

Fig. 3 is a vertical sectional view of a part of a rare gas bulbembodying the novel gas-tight seal of the invention;

Fig. 4 is a fragmentary side elevational view of a sealed rare gas bulb,showing how the same is unsealed to permit discharge of its gas contentinto a receiver; and

Figs. 5 and 6 are fragmentary vertical sectional views of two rare gasbulbs ready for sealing by modified procedures in accordance with theprinciples of the invention.

The principles of this invention are advantageously utilized in filling,sealing and discharging glass bulbs suitable for storing and shippingrare gas, and this application of the invention will be described indetail hereinafter to illustrate one embodiment of such principles.However, it is to be understood that some features of the invention,such as the novel fluid-tight seal for a tube and the procedures forforming and for unsealing such seal, are of more general utility, andthat variations of the exact construction and procedures as disclosedherein are within the scope of this invention.

In accordance with this invention, the novel rare gas container or bulbpreferably has only one connection or tube, which provides both thegas-filling and the gas-Withdrawal passage for the bulb. One open end ofthis tube is integrally secured to an opening in the bulb; its otheropen end is adapted to be connected to evacuating means and to a raregas supply when filling the bulb, and to evacuating means and to areceiver when discharging the rare gas from the bulb. When it has beenfilled with rare gas, the bulb is sealed by a novel gas-tight sealformed within the connecting tube. To assist in forming this seal, thetube desirably is contracted between its ends before joining it to thebulb, which provides a constriction of substantially hourglass shapewithin the tube and outside the bulb. The seal is completed by disposinga solid body of suitable, easily fusible sealin material in gas-tightsealing engagement with the annular internal surface of the narrowestpart of the constriction and also in gas-tight sealing engagement withthe annular internal surfaces adjacent both ends of the narrowest partof the constriction. The sealed gas-filled bulb, when connected to arare gas receiver or customers manifold, may be readily unsealed bysimply externally heating the contracted portion of the tubesufficiently to heat and fuse at least those portions of the fusiblebody of sealing material which sealingly engage the several surfaceportions of the internal constriction.

As illustrated in Fig. 1, the rare gas container or package P desirablycomprises a sphericl glass bulb B provided with a single combined inletand outlet ID to which one open end II of a single glass tube T isintegrally secured so that the tube will extend radially from theoutside of the bulb B. The opposite open end I2 of the tube T may beconnected to suitable means for evacuating, filling and discharging thebulb B through the tube T. Between its ends II and I2, the tube T iscontracted, as by locally heating and stretching the tube before it issecured to the bulb B. This contraction of the tube T provides aconstriction K of substantially hourglass shape inside the tube, whichconstriction has its narrowest section or throat I3 between twoadjoining flaring sections I4 and I5 gradually increasing in diameterfrom the throat I3 to the full inside diameter of the tube. By way ofexample, the tube T may have an outside diameter of about 7 mm. and awall thickness of about 1 mm.; and the constriction K may have a lengthof about 20 mm. and the throat I3 may have a minimum inside diameter ofabout 2 mm.

When the bulb B is to be filled with gas, a solid slug S of suitablefusible sealing material is first inserted through the open end I2 intothe tube T, and the bulb B is so supported that the tube will be heldwith its longitudinal axis inclined to a horizontal plane, preferably ina substantially vertical position, so that the slug S, which is ofsmaller transverse section than the inside of the tube and too large topass through the throat I3, will slide down the tube and be supporteddirectly in contact with the inside of the flaring section I4 above thethroat IS. The shape of the slug S differs from that of the inside ofthe tube T, so as to leave suflicient space for the passage of gasbetween the slug and the tube. As shown in Figs. 1 and 2, for example,the slug S may consist of an elongated solid body of fusible metal, suchas solder, having a lower fusion temperature and a higher thermalcoeflicient of expansion and contraction than the glass forming the tubeT, and the slug S may have an upper portion I6 of square cross-sectionand a pyramidal lower end portion :1 which will project into theconstriction and center the slug axially within the tube and also leavespaces between the slug and the interior surface of the tube for thepassage of gas through the tube into and out of the bulb.

After the slug S is properly positioned in the tube T, the upper openend I2 of the tube is gastightly secured, as by a weld I8, to a glassconduit I9 controlled by a stop-cock 20, for connection to suitablemeans for evacuating the bulb and tube and for supplying rare gas to theevacuated bulb. After the bulb B and tube T have been evacuated by avacuum pump (not shown), rare gas is delivered through the tube T intothe bulb B until the desired gas pressure in the latter is reached. Thenthe slug S is slowly heated and fused so as to gas-tightly seal thefilled container P at the constriction K in the tube T.

While it is being heated and melted, the slug S desirably is supportedvertically with surface portions of its lower end I'I directly engaginginternal surface portions of the constriction K above the throat I3, sothat the fused or molten slug material will flow slowly by gravity downpast the throat I3 while the tube T is held substantially vertically.Immediately after some of the fused slug material begins to flow pastthe throat I3, heating of the slug is discontinued. whereupon the slugmaterial cools and finally solidifies in gas-tight sealing contact withthe internal annular surface of the throat I3 and also in gas-tightsealing contact with both internal annular surface portions of theconstriction sections I4 and I5 adjacent the opposite ends of the throatI3. Under some circumstances it may be desirable to force the moltensealing material into the constriction K by gas pressure, in which eventthe tube T may be held horizontally if desired.

The slug S may be heated to its fusion temperature by various methods.As shown in Fig. 1, the slug may be indirectly heated by positioning ahot slotted soldering iron R around and touching the outside of tube Tadjacent the constriction K, so that its heat is conducted through thewall of the tube to the slug. As the slug melts and flows into thethroat I3, the soldering iron may be gradually lowered until the moltensealing material has reached its proper sealing position, whereupon thesoldering iron is removed. Other heating means, such as a lowtemperature flame, may be used in place of the soldering iron.

The resulting solidified gas-tight seal A, illustrated in Fig. 3,comprises a neck 2| and bulbous heads 22 and 23 integrally connected toopposite ends of the neck 2I. The neck 2i fills the throat I3 andsealingly engages its internal annular surface, and the heads 22 and 23occupy larger portions of the constriction adjacent op-- posite ends ofthe throat and sealingly engage their internal annular surfaces.

It is essential that the seal A remain gas-tight even when the rare gasbulb B and tube T are subjected to temperatures varying greatly above orbelow the temperature of the room in which the seal was formed. This isassured by permitting the molten sealing material to flow to scalingpositions above and below the throat I3 to form the heads 22 and 23 asthe fused sealing material cools and solidifies. Upon discontinuing theapplication of heat thereto, further flow of the sealing material iscontrolled and limited by the viscosity of the molten material and bycapillary action at the sealing surfaces to form the neck 21 and theheads 22 and 23. As the seal A cools to room temperature it contractsaxially more than does the tube T, thus pressing the heads 22 and 23into contact with the surfaces of sections '4 and i5 with sufiicientforce to cause the seal to conform to any irregularities in thesesurfaces and to make gas-tight contact with them.

After the seal A has cooled to room tempera ture and solidified, thetube T is detached from the conduit l9, as by nicking the tube with ahis and then breaking it, whereupon the. filled and sealed rare gaspackage P is ready for storage or shipment with the end I2 of the tube Topen but with the seal A in position in the constriction K.

When the rare gas package P is subjected to atmospheric temperatureslower than the room temperature at which the seal was formed. the seal Atends to contract axially but remains gastlght because the heads 22 and23 are pulled into tighter sealing contact with the internal surfaces ofsections M and I5 adjacent the ends of the throat l3. Thus, at suchlower temperatures a gas-tight seal is assured even though radialcontraction of the seal A may have caused its neck iii to lose sealingcontact with the internal surface of the throat Hi. When the filled andsealed rare gas package is subiected to atmospheric temperatures higherthan the room temperature at which the seal was formed, the seal Aexpands axially and radially, but its radial expansion is much greaterthan that of the glass tube T, thercby maintaining the neck 2| insealing contact with the internal surfe cc of the throat I3. Thus, itappears that tensile and compressive stresses are induced in the seal Aat different atmospheric temperatures and cooperate to maintain a gastight seal. elasticity which is important in maintaining its sealingefficiency in service subject to wide temperature changes.

The slug S and resulting seal A may consist of any fusible materialhaving a melting point or fusion temperature lower than the vfusiontemperature of the material of the tube T and also having a higherthermal coefll ient of expansion and contraction than the material oftube T. Preferably the slug S and seal A consist of a fusible metalhaving a fusion temperature lower than the temperature at which theglass of the tube T softens appreciably. and. having a thermalcoefificient of expansion and contraction higher than that of such glassto maintain gas-tight sealing engagement of the seal A with internalsurfaces of the constriction K over a substantial range of atmospherictemperatures. Low melting bismuth base alloys have been foundadvantageous as materials for forming the slug S. For example. a bismuthsolder slug consistin of a metal alloy having a melting point of 113 C.and containing about 40% bismuth, 40% lead and tin has been usedsuccessfully. Another suitable metal is Wcods alloy which contains about50% bismuth, 12.5% cadmium, lead and 12.5% tin, and has a melting pointof 53 C. When the bismuth. 40% lead and 209: tin solder is used theratio of the length of the con-- striction K to its minimum diameter maybe tween 8 to l. and 12.5 to 1. Both sealing alloys described above havea thermal coefilcient of expansion and contraction of about 27 10" C. Incontrast, commercial glasses suitable for making the bulb B and the tubeT have softening points ranging between 500" C. and 1-510 C. and thermalcoefiicients of expansion and contraction ranging from 3 l0 W C. toIZXIO C. Tests have demonstrated that gas-tight seals made at 70 F. withbismuth solder in accordance with The seal A also has some decree of 6this invention remain gas-tight at -40 F. and at 212 F.

The rare gas content of the sealed gas package P y be readily releasedand discharged at will into a suitable receiver or manifold. Asillustrated in Fig. 4. the open. end 42 of the tube T is firstgas-tightly connected, as by a weld 25, to a glass conduit 26 leadingthrough a stop-cock Zl to suitable evacuating, means and a suitable raregas receiver. The cock 2'! is then opened and the portion of theconnection between the seal A and the as receiver is evacuated to theatmosphere to eliminate contaminating gas. Thereupon, a suitable sourceof heat, such as the flame of a lighted match M or any other heatingmedium. is applied to and moved around the outside of the tube Tadjacent the seal heat melts at least those parts of the seal A whichengage the inside surface of the constriction K and loosens the sealsufficiently to unseal the pa ck- .1 P. When the seal A has becomesufiicienily u ed to pass through the throat l3, the pressure of the gasin the bulb B blows the seal A from its sealing position up into theupper portion of tube T and the rare gas from the bulb R then passesfreely around the seal and through the connecting conduit 28 into thereceiver.

It will be evident that a gas-tight seal embodying this invention may beformed by methods which involve variations of the preference sealformingprocedure described above.

For example, as shown in Fig. 5, the sealing slug S may be inserted intothe bulb B before constricted tube T is united to the opening in thebulb B; and for this sealing operation the bulb B is held uppermost withthe tube T extending substantially vertically downwardly and the sealingslug S resting directly on the flaring constriction section l5, so thatthe pointed end of the slug extends into the throat l3. Then the seal Amay be formed in the constriction K by the heating and cooling stepspreviously described. As another alternative, a bulb B" and tube T" maybe constructed so that the throat l3" of the constriction K" is locatedat the joint between the bulb and the tube as in Fig. 6; and in order toform a seal A in this constriction, a sealing slug S" is placed in thebulb B" before the tube is joined to the bulb. Then the bulb B is helduppermost with the tube T extending vertically downward and the pointedend of the slug S" projecting into the throat of the constriction.Completion of the operation to form the seal may be accomplished by theheating and cooling steps previously described.

Seals in accordance with the principles of the invention are simple,easily formed, and much more economical than the seals formerly used inrare gas packages. For example, the cost of. the novel seal is less thanhalf as great as that of the formerly used glass sealing capsule, whichconstituted an appreciable portion of the cost of the whole package.Moreover, rare gas packages having the novel seals are not subject topremature breakage when the seals are being opened. These important andbeneficial advantages are obtained while providing a seal which isgas-tight over a wide temperature range. and which is easily broken whengas is to be discharged from a package such as a rare gas bulb.

It is evident that variations in the above described seal and methodsfor making and breaking the seal can be made within the scope of theinvention. For example, the seal is effective at temperatures at orbelow the room temperature at which it is formed even though the metalmay not initially have sealingly engaged the narrowest portion of theconstriction.

We claim:

A method of filling, sealing and discharging rare gas in a. glass bulbhaving integrally connected thereto one end of a single glass tubeconstituting both a gas-filling and a gas-withdrawal passage and havinga contracted portion outside said bulb providing an internalconstriction in said tube, said method comprising inserting, through theother end of said tube and adjacent said constriction, a slug or fusiblesealing metal having a lower fusion temperature and a higher thermalcoeflicient of expansion and contraction than the glass of said tube;evacuating said bulb through said tube; filling rare gas through saidtube into such evacuated bulb; sealing said tube and such filled bulb byapplying sufiicient heat to the outside of the contracted portion ofsaid tube to transfer heat to and fuse said slug while holding said tubesubstantially vertical, to cause fused portions of said slug to flow bygravity into sealing engagement with the internal annular surface of thenarrowest part of said constriction and also into sealing engagementwith the internal annular surface portions of said tube adjacent theopposite ends of said narrowest JOHN N. BURDICK. HARVEY E. KINNE.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 908,378 Bastian et a1. Dec. 29, 1908 1,726,111 Loewe Aug. 27,1929 1,911,410 Valverde May 30, 1933 1,914,634 Eden et a1 June 20, 19332,202,337 Cohn May 28, 1940 2,262,176 Geiger et a1. Nov. 11, 19412,419,112 Brandt, Jr. Apr. 15, 1947

